Originally Posted by wallcraft
The .acsm file is a small transfer file that contains the encryption codes necessary for downloading the actual PDF. All you should need to do is open the .acsm file using Adobe Digital Editions. Usually, when you install ADE it tells your web browser to do this automatically when it sees an .acsm file.
I also believe that version 3 of the Sony Library software will work as well (at least, the Mac version does). Just right-click on the .ascm file, and "Open with" either program.